On Mon, Nov 7, 2011 at 8:17 AM, Johan Tibell wrote:

On Mon, Nov 7, 2011 at 7:53 AM, Ben Gamari wrote:

...

With GHC 1ece7b27a11c6947f0ae3a11703e22b7065a6b6c zlib fails to build, apparently due to Safe Haskell (bug 5610 [1]). The error is specifically,

$ cabal install zlib Resolving dependencies... Configuring zlib-0.5.3.1... Preprocessing library zlib-0.5.3.1... Building zlib-0.5.3.1... [1 of 5] Compiling Codec.Compression.Zlib.Stream ( dist/build/Codec/Compression/Zlib/Stream.hs, dist/build/Codec/Compression/Zlib/Stream.o )

Codec/Compression/Zlib/Stream.hsc:857:1:    Unacceptable argument type in foreign declaration: CInt    When checking declaration:      foreign import ccall unsafe "static zlib.h inflateInit2_" c_inflateInit2_        :: StreamState -> CInt -> Ptr CChar -> CInt -> IO CInt

Codec/Compression/Zlib/Stream.hsc:857:1:    Unacceptable argument type in foreign declaration: CInt    When checking declaration:      foreign import ccall unsafe "static zlib.h inflateInit2_" c_inflateInit2_        :: StreamState -> CInt -> Ptr CChar -> CInt -> IO CInt

Codec/Compression/Zlib/Stream.hsc:857:1:    Unacceptable result type in foreign declaration: IO CInt    Safe Haskell is on, all FFI imports must be in the IO monad    When checking declaration:      foreign import ccall unsafe "static zlib.h inflateInit2_" c_inflateInit2_        :: StreamState -> CInt -> Ptr CChar -> CInt -> IO CInt ...

This is a little strange since,

 a) It's not clear why Safe Haskell is enabled  b) The declarations in question seem to be valid

Does this seem like a compiler issue to you?

This is due to a change in how FFI imports and newtypes work. GHC was recently changed to not allow you to use newtypes in FFI imports unless the constructor of the newtype is in scope. This broke quite a few libraries. I have patched a few of them and I've sent a patch to the zlib maintainer.

This seems like a big change. Where should I be watching to know about this ahead of time? I bet I have to fix some of my packages. Thanks, Jason

On Monday 07 November 2011, 21:06:17, Jason Dagit wrote:

On Mon, Nov 7, 2011 at 8:17 AM, Johan Tibell wrote:

...

This is due to a change in how FFI imports and newtypes work. GHC was recently changed to not allow you to use newtypes in FFI imports unless the constructor of the newtype is in scope. This broke quite a few libraries. I have patched a few of them and I've sent a patch to the zlib maintainer.

This seems like a big change.

But it introduces conformance with the report: http://www.haskell.org/onlinereport/haskell2010/haskellch8.html#x15-1540008.... (sec. 8.4.2, Foreign Types) "Consequently, in order for a type defined by newtype to be used in a foreign declaration outside of the module that defines it, the type must not be exported abstractly." Previous behaviour violated that, hence the change.

Where should I be watching to know about this ahead of time? I bet I have to fix some of my packages.

Thanks, Jason